This site is more of a gay fitness, health, and workout buddy site. A4A is a total hookup site, I have met one legit friend from there. Manhunt is all older, heavier guys. OkCupid has a lot more serious guys and is easy to make friends on. Grindr..... Trashy.
I think it depends on your city and its makeup. For me, Match.com is by far my best site for meeting guys. I've made some friends through A4a actually, although I had to wade through a lot of debris to find them. I'm more into guys who are a little rougher around the edges and in Austin, Okcupid tends to attract more of the "shy boy next door" type guy so it doesn't work so well for guys like me. But I think the match feature on there is cool.